The present invention relates to an ophthalmic prosthetic device and more particularly to an anti-reactive coated intraocular lens.
As is well known in the field of ophthalmology, an intraocular lens, when surgically implanted, is designed to replace a previously or simultaneously removed cataractous lens. In addition, it is contemplated that such lenses can be placed in the phakic eye to compensate for refractive errors. The optical portion of such lenses may be of glass; a silicone polymer; an acrylic polymer, such as polymethyl methacrylate or polyhydroxyethyl methacrylate; or any combination thereof. The optical portion of the intraocular lens may also be made of copolymers of methyl methacrylate and ethyl acrylate or acrylic type monomers; copolymers of siloxanylalkyl acrylates and methacrylates; copolymers of fluoroacrylates and methacrylates; polysulfones; and polymers and copolymers of 2-hydroxyethyl methacrylate, glyceryl methacrylate, 2-hydroxypropyl methacrylate, methacrylic acid, acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid, styrene sulfonic acid, acrylamide, methacrylamide, N-vinylpyrrolidone, diacetone acrylamide, 2-vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine, N-(2-methacryloyloxyethyl)-N,N-dimethylamine and N-(3-acrylamidopropyl)-N,N-dimethylamine. It is also possible for the intraocular lens to contain an ultraviolet absorber. These are presumably biologically neutral materials. The optical portion may have supports of the same nature, or may be supported by loops made of nylon, polypropylene, metal, polymethyl methacrylate or methyl methacrylate copolymers with other acrylic monomers.
An intraocular lens is small, with most anterior and posterior chamber lenses having an overall diameter of approximately 12-14 mm, if in a single piece of glass, silicone or plastic, with an optical diameter of 4 mm to 6 mm. Tip-to-tip diameters of looped anterior and posterior chamber lenses are approximately 12 mm to 15 mm. Iris support lenses usually have 8-10 mm loop diameters. The center thickness and posterior radii of the optical portion vary according to the power desired and the material utilized. An intraocular lens may weigh up to 25 mg in air, or 0.5 mg to 4 mg in aqueous medium. The intraocular lenses are commercially available from a variety of companies throughout the world.
Although the implantation of intraocular lenses has constituted an appreciable surgical advance, their use can still be improved upon significantly. For example, implantation of an intraocular lens may cause immediate or late damage to the corneal endothelium, immediate or late inflammatory responses to the anterior segment of the eye, immediate or late inflammatory responses to the posterior segment of the eye, and immediate or late secondary fibrosis and/or neovascularization. All in all, flare, white cells, vitreous reaction, cystoid macular edema, hypopyon, uveitis and secondary glaucoma are occurrences that may be present immediately or in a delayed manner after implantation and have become an ever-increasing problem.
When an intraocular lens is inserted into the eye, the mechanics of insertion may lead to temporary adhesion of the lens to delicate intraocular structures and damage to these structures ensues either immediately or is manifested in the long term. When in position, lenses may cause adhesions and fibrosis of a progressing nature, damaging intraocular tissues and making removal of such a lens a complex, dangerous surgical procedure. In particular, if such lenses are used in phakic eyes, damage to the clear lens may result negating the benefits of the operation. Coating such a lens with a coating material which would fill in the microscopic crevices that are present, no matter how well the lens is polished, softens the surface, changes its surface tension, and changes the contact angle. Such a coating will alter the abrasive potential of a lens and reduce the trauma of insertion and maintenance. Secondly, if this coating is physiologically inert and acts as a barrier, it can reduce the inflammatory potential of intraocular lenses and the dangerous sequelae resulting therefrom. Further, the coated lens may act as a therapeutic agent and may be used to elute materials that act as therapeutic agents to prevent and treat secondary reactions mentioned above.
U.S. Pat. No. 4,170,043 discloses coated intraocular lenses made of an acrylic resin wherein the coating is to prevent adhesion of the intraocular lens to the corneal endothelium, the coating being polyvinylpyrrolidone, polyvinyl alcohol, hydroxypropyl cellulose, hydroxypropyl methylcellulose, dextran, hydroxyethyl starch, methylcellulose or Jaguar (guar gum). However, some of these coatings caused inflammatory reactions and proved to be unsatisfactory in clinical practice.
Published West German patent application No. 2,556,665 discloses coated intraocular lenses wherein the coating is a silicone rubber, such as methyl or methylphenyl siloxane. However, such siloxane polymers cannot be crosslinked using ultraviolet light irradiation plus either a photosensitizer or a peroxide and hence the uncrosslinked siloxane coatings smudge upon contact with another surface.
U.S. Pat. No. 4,240,163 discloses coated intraocular lens wherein the coating is a compatible medicament. However, such coating materials cannot be gradually and controllably released from the intraocular lens surface with time, but rather they are generally rapidly released therefrom in the presence of the aqueous humor occupying the anterior and posterior chambers of the eye.